The secret to the perfect cup of coffee?

Kieran Davey

Mathematicians are a step closer to answering one of life’s biggest questions - how to make the perfect cup of coffee.

A researcher from the University of Portsmouth has discovered that the size of the coffee grain is the most important factor in creating a cuppa.

Co-author Dr William Lee, who leads the university’s industrial mathematics group, said a better understanding of the physics and chemistry of coffee brewing could lead to better designed coffee machines.

He said: ‘What makes the best coffee is hideously complicated – from the shape of the filter, to the scale of a single grain, to the flow rate of water and which machine or tool is used, there are an enormous number of variables.

‘But maths is a way of revealing hidden simplicity. ‘By using mathematical analysis, we can begin to tell the story of which elements and in what order lead to the best coffee – we are now one step closer to the perfect cup of coffee.’

Dr Lee co-wrote the research - which has been published today - when he was at the University of Limerick.

The team hope to develop a complete theory of coffee brewing that could be used to inform the design of filter coffee machines in the same way that industry uses the theories of fluid and solid mechanics to design aeroplanes and racing cars.

Dr Lee said: ‘One of the many challenges that have to be overcome to develop such a theory is to understand the effect the grind size has on the extraction of coffee.

‘Our model shows that this can be understood in terms of the grind size controlling the balance between rapid extraction of coffee from the surface of grains and slow extraction from the interior of coffee grains.

‘This not only explains qualitatively why grind size plays such an important role in determining the taste of coffee but also quantifies that relationship through formulas. ‘These formulas could allow fine tuning the design of a coffee machine for a particular grind size.’